Targets for Obesity

Obesity is a complex, multifactorial disease involving dysregulation of energy homeostasis, appetite control, nutrient metabolism, and neuroendocrine signaling. The molecular targets identified here provide mechanistic insights into the pathogenesis of obesity by representing key nodes in the regulation of appetite (central and peripheral), nutrient absorption and metabolism, and hormone signaling. Understanding these targets facilitates the identification of novel therapeutic strategies, such as appetite suppressants, metabolic modulators, and agents that influence nutrient digestion or absorption. Collectively, these targets are instrumental in supporting drug discovery and development, as they represent validated or emerging points of intervention for pharmacological and biological therapies. Their study also improves our understanding of disease progression, comorbidity risk, and patient stratification, enabling more precise and effective treatment approaches for obesity.

Central Appetite Regulation

This category includes targets that directly modulate appetite and satiety through central nervous system pathways, primarily within the hypothalamus and related brain regions. These targets regulate feeding behavior, energy expenditure, and neuroendocrine signaling, and are directly implicated in the pathogenesis of obesity through their influence on food intake and reward pathways. Key targets in this category are 5-hydroxytryptamine receptor 2C (HTR2C), hypocretin receptor 2 (HCRTR2), solute carrier family 6 member 4 (SLC6A4), opioid receptor kappa 1 (OPRK1), opioid receptor mu 1 (OPRM1), and trace amine associated receptor 1 (TAAR1). Dysregulation or genetic variation in these targets can lead to hyperphagia, altered satiety, and increased susceptibility to obesity.

5-hydroxytryptamine receptor 2C (HTR2C)

HTR2C is a G protein-coupled serotonin receptor predominantly expressed in the hypothalamus, with seven transmembrane domains. It is regulated by serotonergic signaling and modulates the release of pro-opiomelanocortin (POMC), influencing melanocortin pathways that suppress appetite. Genetic variants and functional deficits in HTR2C are associated with hyperphagia and severe obesity, as evidenced by both human and rodent studies. HTR2C agonists (e.g., lorcaserin) have demonstrated clinical efficacy in reducing food intake and body weight, highlighting its therapeutic potential. It is a validated drug target, with its modulation resulting in significant weight loss in clinical trials.

Hypocretin receptor 2 (HCRTR2)

HCRTR2 is a G protein-coupled receptor for orexins (hypocretins), neuropeptides that stimulate arousal, wakefulness, and food intake. It contains seven transmembrane domains and is primarily expressed in hypothalamic nuclei. HCRTR2 activation increases appetite and energy expenditure, while loss-of-function mutations lead to narcolepsy and reduced food intake. Pharmacological antagonism of orexin signaling is being explored for metabolic and sleep disorders. Genetic and pharmacological data support a role for HCRTR2 in obesity susceptibility, particularly through its effects on hedonic feeding and energy balance.

Solute carrier family 6 member 4 (SLC6A4)

SLC6A4 encodes the serotonin transporter (SERT), which is responsible for reuptake of serotonin from synaptic clefts. It consists of 12 transmembrane domains and is tightly regulated by phosphorylation and protein interactions. SERT function modulates serotonergic tone, impacting appetite and mood. Polymorphisms in SLC6A4 are associated with altered eating behavior and obesity risk. SERT inhibitors (SSRIs) can affect weight, underscoring the transporter’s role in appetite regulation and its indirect impact on obesity.

Opioid receptor kappa 1 (OPRK1)

OPRK1 is a G protein-coupled receptor involved in modulating reward, stress, and feeding behavior. It has seven transmembrane domains and is regulated by endogenous dynorphins. Kappa opioid signaling can promote dysphoric states and influence preference for palatable food, contributing to compulsive eating and obesity. Animal studies show that OPRK1 antagonism reduces binge eating and body weight, supporting its relevance as a therapeutic target.

Opioid receptor mu 1 (OPRM1)

OPRM1 encodes the mu-opioid receptor, a key regulator of reward and hedonic aspects of feeding. The receptor is a seven-transmembrane GPCR, regulated by phosphorylation and beta-arrestin-mediated internalization. Activation of OPRM1 enhances the intake of palatable foods and is linked to obesity in both animal models and humans. OPRM1 antagonists (e.g., naltrexone, as part of bupropion/naltrexone therapy) are approved for obesity treatment, demonstrating clinical utility and mechanistic relevance.

Trace amine associated receptor 1 (TAAR1)

TAAR1 is a GPCR responsive to trace amines and amphetamine-like compounds. It is expressed in the brain and modulates monoaminergic neurotransmission, including dopamine and serotonin systems. TAAR1 activation suppresses food intake and body weight in preclinical models, implicating it as a potential anti-obesity target. Its role in central energy balance and reward circuitry is under active investigation.

Peripheral Hormone and Peptide Signaling

This category includes targets that modulate the hormonal control of glucose and lipid metabolism, insulin secretion, and energy homeostasis. These targets are critical in the pathogenesis of obesity through their regulation of nutrient partitioning, satiety signaling, and metabolic rate. Key targets are glucagon like peptide 1 receptor (GLP1R), gastric inhibitory polypeptide receptor (GIPR), glucagon receptor (GCGR), and insulin (INS). Dysregulation of these pathways leads to hyperglycemia, hyperinsulinemia, and impaired satiety, contributing to obesity and its metabolic complications.

Glucagon like peptide 1 receptor (GLP1R)

GLP1R is a class B GPCR expressed in pancreatic beta cells, the brain, and gastrointestinal tract. It mediates the effects of GLP-1, an incretin hormone that enhances glucose-dependent insulin secretion, inhibits glucagon release, delays gastric emptying, and reduces appetite. Structural features include a large extracellular domain for ligand binding. GLP1R agonists (e.g., liraglutide, semaglutide) are approved for obesity and type 2 diabetes, with robust weight loss effects (up to 15% in clinical trials, e.g., STEP 1, NEJM 2021). GLP1R is a validated therapeutic and biomarker target for obesity.

Gastric inhibitory polypeptide receptor (GIPR)

GIPR is a class B GPCR for GIP, an incretin hormone that stimulates insulin secretion postprandially. It is expressed in pancreatic beta cells and adipose tissue. GIPR signaling promotes nutrient storage and adipogenesis, and its dysregulation is implicated in obesity and insulin resistance. Dual GLP-1/GIPR agonists (e.g., tirzepatide) have demonstrated superior weight loss compared to GLP-1R agonists alone (SURMOUNT-1, NEJM 2022), confirming GIPR’s significance in obesity therapeutics.

Glucagon receptor (GCGR)

GCGR is a class B GPCR that mediates the effects of glucagon, promoting hepatic glucose production and lipolysis. It is primarily expressed in the liver. Overactivation of GCGR can exacerbate hyperglycemia and promote weight loss, but also contributes to metabolic dysregulation in obesity. Antagonists and dual agonists (GLP-1/GCGR) are under investigation for obesity and diabetes. GCGR modulation alters energy expenditure and nutrient partitioning, influencing obesity risk.

Insulin (INS)

Insulin is a peptide hormone produced by pancreatic beta cells, consisting of A and B chains linked by disulfide bonds. It regulates glucose uptake, lipogenesis, and inhibits lipolysis. Chronic hyperinsulinemia and insulin resistance are hallmarks of obesity and metabolic syndrome. Insulin acts via the insulin receptor tyrosine kinase, activating PI3K-Akt and MAPK pathways. Therapeutic modulation of insulin signaling (sensitizers, analogs) is critical in managing obesity-related metabolic dysfunction.

Lipid and Energy Metabolism

Targets in this category are involved in the synthesis, breakdown, and absorption of dietary fats, as well as the regulation of energy storage. They play a direct role in the development of obesity by influencing caloric intake, fat absorption, and adipose tissue expansion. Key targets include fatty acid synthase (FASN), diacylglycerol lipase alpha (DAGLA), pancreatic lipase (PNLIP), and lipase F, gastric type (LIPF). Inhibition or modulation of these enzymes can reduce energy absorption or alter lipid metabolism, offering therapeutic potential for obesity.

Fatty acid synthase (FASN)

FASN is a large, multifunctional enzyme complex responsible for de novo synthesis of long-chain fatty acids from acetyl-CoA and malonyl-CoA. It contains multiple catalytic domains (e.g., acyl carrier, ketoacyl synthase). FASN is upregulated in adipose tissue in obesity and is regulated by insulin and SREBP-1c. Inhibition of FASN reduces adiposity and improves metabolic profiles in preclinical models. FASN inhibitors are in early-phase clinical development for obesity and NASH.

Diacylglycerol lipase alpha (DAGLA)

DAGLA is a membrane-associated enzyme that hydrolyzes diacylglycerol to produce 2-arachidonoylglycerol (2-AG), a key endocannabinoid. It contains a serine hydrolase domain. DAGLA activity modulates endocannabinoid signaling, which influences appetite, adipogenesis, and energy balance. Excessive endocannabinoid tone is linked to hyperphagia and obesity. Pharmacological inhibition of DAGLA is being explored as an anti-obesity strategy.

Pancreatic lipase (PNLIP)

PNLIP is a serine hydrolase secreted by the pancreas, essential for hydrolyzing dietary triglycerides into absorbable free fatty acids and monoglycerides. It consists of a catalytic triad and a lid domain. Orlistat, a PNLIP inhibitor, is an approved anti-obesity drug that reduces fat absorption by ~30%, leading to weight loss (XENDOS study, Lancet 2004). PNLIP is a validated therapeutic target for obesity.

Lipase F, gastric type (LIPF)

LIPF is a gastric lipase with a serine hydrolase domain, initiating the digestion of dietary triglycerides in the stomach. It complements pancreatic lipase activity. LIPF contributes to overall fat absorption and energy intake, and its activity may influence susceptibility to obesity, particularly in early life. Inhibition of gastric lipase reduces fat absorption, representing a potential anti-obesity approach.